As disclosed in U.K. patent application No. 2 065 655 A (Upjohn) and Japanese Kokai Patent Application No. SHO-57[1982]-16830 (Sagami), it is known to prepare halobiphenyl compounds by pseudo-Gomberg reactions wherein an aminohalobenzene is diazotized with an alkyl nitrite and then coupled with a benzene compound. Except when a copper catalyst has been employed, these reactions have typically utilized elevated diazotization temperatures, e.g., 20.degree.-80.degree. C., preferably about 65.degree. C., although (1) U.S. Pat. No. 3,992,459 (Utne et al.) shows that lower diazotization temperatures can be used for such reactions when the amine has been protonated before being contacted with the alkyl nitrite and a catalyst is employed, and (2) the use of lower diazotization temperatures for the reactions between non-halogenated aromatic amines and isoamyl nitrite is disclosed in Hassanaly et al., Bull. Soc. chim., 1974, pp. 560-562, and Vernin et al., Bull. Soc. chim., 1974, pp. 1079-1084.
A variety of haloaminobenzenes is taught to be utilizable in the Upjohn processes, including compounds having a cyano group attached to the aromatic ring. However, the amino compounds of the working examples are limited to dihaloanilines, and Upjohn does not suggest how their teachings could be modified to permit an efficient coupling of benzene compounds and substituted aminohalobenzenes outside the scope of their invention, such as aminohalobenzenes having a cyano group indirectly attached to the aromatic ring through an alkyl group. Such substituted aminohalobenzenes have been found to lead to much lower yields of biphenyl compounds than the aminobenzenes taught by Upjohn.
Sagami prophetically teaches that aminohalobenzeneacetonitriles may be used in their aryl coupling processes but--like Upjohn--do not suggest how the teachings of their working examples could be modified to permit an efficient coupling of such compounds with benzene compounds, and particularly do not suggest how such an efficient coupling could be accomplished in the absence of a copper catalyst.